The invention relates in general to an arrangement for monitoring or detecting a physical condition such as breakage or elongation of a structural part by means of at least one light conduit, the inlet and outlet portions of which are connectable to a light source and a light receiver, respectively, to monitor its light conductivity.
With increasing complexity of modern constructions, motor vehicles and machines, an increased need is felt for providing means for monitoring the changes of physical conditions of certain structural elements, whereby the monitoring should be simple, fast and performable without disassembly of the whole structure. Another field of application for such monitoring means is in protection against break-ins and theft.
From German publication No. 2,937,824 a method is known for detecting breakage of component parts which are under tensile load. In this known method, light-conductive fibers are mounted or embedded in the zones of the component part which are susceptible to breakage, whereby the light conductivity of the light-conductive fibers is continuously or intermittently checked.
In this publication, however, there is no suggestion how to adjust the employed light conductors to different qualities of the component parts to be monitored.
In German patent application No. 3,015,391 it has also been proposed to reinforce the light-conductive fibers and connect the same to the structural part by means of elastic envelopes.
This embodiment is suitable for structural parts whose critical deformation is greater than the breaking elongation of the applied light conductors; only in this case is it assured that the light conductors rupture at a definite critical elongation of the structural element, thus yielding the desired indication that the structural part is overloaded.